pythonz, an active fork of pythonbrew, makes this a breeze. You can install a version with:
# pythonz install 2.7.3
Then set up a symlink with:
# ln -s /usr/local/pythonz/pythons/CPython-2.7.3/bin/python2.7 /usr/local/bin/python2.7
# python2.7 --version
Python 2.7.3